Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The description discloses that the tool returns the updated cart, which adds value beyond annotations. Annotations already indicate write (readOnlyHint=false) and non-destructive (destructiveHint=false), and the description reinforces these aspects.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single efficient sentence with inline parameter notes, no redundancy, and front-loads the core purpose.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's moderate complexity (4 parameters, 2 required) and the presence of an output schema, the description sufficiently covers the return value and parameter sources, though it could hint at side effects like price updates or inventory checks.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With 100% schema description coverage, the description does not add significant new meaning beyond the schema, though it reiterates key constraints (e.g., 'from search/get_product', 'must be one of the product's sizes'). Baseline of 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action ('Add a product to the user's cart') and resource ('cart'), distinguishing it from siblings like 'add_custom_to_cart' or 'cart_update'.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides guidance on required arguments (good_id, size) and optional ones (fabric, qty) with defaults, indicating when to use them. It lacks explicit when-not-to-use or alternatives, but the context is clear.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.